A TI{2A-C-int::GAL4(21-881)} cassette has been inserted in-frame into the endogenous Ret locus. The presence of the 2A peptide results in the C-int::GAL4(21-881) hemidriver being expressed as a separate protein under the control of endogenous Ret regulatory sequences. The sgRNA sequence used to target the gene was: CCATCCGCAGCACTTGGAAC.